1. Field of the Invention
The present invention relates generally to fluid reaction surfaces, and more specifically to a turbine vane with cooling of the fillet region.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, especially an industrial gas turbine engine, a turbine section includes a plurality of stages of stator vanes and rotor blades to extract mechanical energy from the hot gas flow passing through the turbine. The efficiency of the turbine, and therefore of the engine, can be increased by increasing the turbine inlet temperature of the gas flow from the combustor. However, the temperature is limited to the material properties of the first stage turbine airfoils—the stator vanes and rotor blades —since the first stage airfoils are exposed to the hottest gas flow.
Passing cooling air through the airfoils can also allow for a higher gas flow temperature since the cooled airfoils can be exposed to higher temperatures. Complex convection and film cooling circuits have been proposed in the prior art to maximize the cooling effectiveness of the internal cooling circuits. Increasing the cooling ability while using less cooling air will provide higher efficiency. FIGS. 1 and 2 show one prior art vane cooling circuit which includes a 5-pass aft flowing serpentine cooling circuit, two ID (inner diameter) and OD (outer diameter) turns, skew trip strips for all of the serpentine cooling passages, cooling air feed through the airfoil leading edge passage from OD endwall, trailing edge discharge cooling slots, and a jumper tube for delivering cooling air to the inner seal housing, all of which provides for an efficient cooled turbine vane. See U.S. Pat. No. 5,488,825 issued to Davis et al on Feb. 6, 1996 and entitled GAS TURBINE VANE WITH ENHANCED COOLING, the entire disclosure being incorporated herein by reference. In the prior art FIG. 1 blade, the root and blade tip turns in the serpentine circuit take place within the airfoil between the endwalls of the vane.
However, the stator vane cooling circuit of FIGS. 1 and 2 has some disadvantages. For the vane trailing edge OD fillet region, due to inadequate cooling for the junction of the airfoil trailing edge fillet versus the endwall location, the vane aft fillet region experiences a low LCF (low cycle fatigue) life. Also, at the vane trailing edge fillet location, a higher heat transfer coefficient or heat load onto the downstream fillet location exists due to the trailing edge wake effect. On top of a higher heat load onto the airfoil fillet location due to the stress concentration issue, the cooling hole for the airfoil trailing edge OD section cannot be located high enough into the vane OD section fillet region to provide proper convective cooling. Cooling of this particular airfoil trailing edge fillet region becomes especially difficult.
It is therefore an object of the present invention to provide for a stator vane with improved cooling of the airfoil trailing edge fillet region.
It is another object of the present invention to provide for a turbine vane with an aft fillet region with an improved LCF life over the cited prior art reference.